Supplements: To Take or Not to Take, That Is the Question
Dietary Supplements 101
Too Much of a Good Thing
Supplements: Recommended Intake Levels of Some Supplements and Known Risks Associated With Excessive Amounts
|Vitamin or Mineral||Why You Need It||Recommended Dose (for adults, ages 19-50)||Tolerable Upper Intake Level (UL)||What Happens if You Overdo It||Good Food Sources|
|Vitamin A||Vision, growth, and immune function||900 micrograms per day (µg/d) for men (equivalent to 2,997 International Units), 700 µg/d for women (2,333 IU/d)||3,000 µg/d (10,000 IU/d)||Too much may cause hair loss, nausea, and vomiting, and may increase the risk of bone fracture. Very high intakes can cause liver disease and fetal malformations.||Preformed vitamin A sources include fortified cereal, eggs, and dairy products; Provitamin A carotenoids (like beta-carotene), found in deep orange and dark green fruits and vegetables|
|Vitamin B6||Protein metabolism, neurotransmitter formation, red blood cell function, and hormone function||1.3 milligrams per day (mg/d)||100 mg/d||If taken at very high doses, may result in painful neurologic symptoms and difficulty walking.||Fortified cereals, beans, meat, poultry, fish, and some fruits and vegetables|
|Folic acid (folate)||DNA metabolism as well as the metabolism of several important amino acids||400 µg/d||1,000 µg/d||High doses, while safe in themselves, may mask symptoms of, the rare disease, pernicious anemia allowing it to progress unchecked.||Fruits and vegetables, fortified grain foods|
|Niacin||Necessary for energy metabolism||16 mg/d for men, 14 mg/d for women||35 mg/d||In doses fifty times higher than the tolerable upper intake level, can damage the liver and cause severe gastrointestinal problems.||Meat, poultry, fish, fortified cereals, legumes, milk, and seeds|
|Vitamin C||It is required for the synthesis of collagen and the neurotransmitter norepinephrine||90 mg/d for men, 75 mg/d for women||2,000 mg/d||Generally safe, but at high doses can cause diarrhea and might increase risk of urinary tract stones.||Citrus fruits|
|Vitamin D||It helps to form and maintain strong bones, plus is needed to maintain blood levels of calcium and phosphorus||15 µg/d||100 µg/d||Continuous very high intakes might lead to damage to the heart, blood vessels and kidneys due to calcification.||Fatty fish (herring, salmon, sardines), eggs from hens that have been fed vitamin D, and fortified milk; exposure to sunlight provides another important source|
|Iron||An essential component of hundreds of proteins involved in the transport and storage of oxygen||8 mg/d for men, 18 mg/d for women||45 mg/d||Can poison a child, causing nausea, vomiting, lethargy, fever, difficulty breathing, coma, and even death; in adults excess iron is theorized to increase risk of heart disease.||Lean red meats, shellfish, legumes, dried fruit, and green leafy vegetables (Note: iron from non-meat sources is best absorbed when vitamin C is also present)|
|Selenium||Necessary for the function of numerous enzymes||55 µg/d||400 µg/d||Toxic effects of overdosage include hair and nail brittleness and loss, gastrointestinal disturbances, skin rashes, fatigue, irritability, and nervous system abnormalities.||Organ meats, seafood, and grains|
The Bottom Line
- A multivitamin cannot provide adequate calcium, and for this reason many people could benefit from a separate calcium supplement.
- Be wary of unfounded medical claims for dietary supplements.
- Talk to your doctor about all supplements you take, including concentrations and amounts.
- Keep supplements out of the reach of children.
National Institutes of Health, Office of Dietary Supplements http://ods.od.nih.gov
United States Food and Drug Administration, Center for Food Safety and Applied Nutrition http://vm.cfsan.fda.gov
Canadian Council on Food and Nutrition http://www.ccfn.ca
Dietitians of Canada http://www.dietitians.ca/
Dietary supplement fact sheet: vitamin A. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/Vitamina-HealthProfessional/. Accessed June 2, 2012.
Dietary supplement fact sheet: vitamin B6. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/. Accessed June 2, 2012.
Dietary supplement fact sheet: vitamin C. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/. Accessed June 2, 2012.
Dietary supplement fact sheet: vitamin D. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/vitamind-HealthProfessional/. Accessed June 2, 2012.
Dietary supplement fact sheet: iron. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/iron-HealthProfessional/. Accessed June 2, 2012.
Dietary supplement fact sheet: folate. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/folate-HealthProfessional/. Accessed June 2, 2012.
Dietary supplement fact sheet: selenium. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/. Accessed June 2, 2012.
Vitamin B3. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/biomedical-libraries/natural-altnerative-treatments. Updated August 2011. Accessed June 2, 2012.
- Reviewer: Brian Randall, MD
- Review Date: 06/2012 -
- Update Date: 06/02/2012 -